More than half of Liberal Democrat MPs, including two cabinet members and eight junior ministers, are on record as opposing plans by David Cameron to water down security of tenure for new social housing tenants.

Cameron suggested the idea of fixed-term tenancies for new tenants last week, and the housing minister, Grant Shapps, continued to defend the plan this weekend, saying lifetime tenancies did not make sense.

Speaking on Sky News today, he said: "Just because somebody needs a home at one point does not mean that they will always needs that home subsidised by the state."

He for the first time suggested that it might be for a housing association, or house builder, to decide whether to continue with lifetime tenancies in their properties, or instead restrict them to a limited period such as 15 years.

Shapps said it was important to do something about the allocation system so that the doubling of the council house waiting list could be tackled.

He also moved to deal with the argument of some Liberal Democrats that not enough affordable social housing is being built by emphasising his policy of allowing councils to keep double the consequent council tax income from any new homes built.

While Shapps will write to all councils emphasising the incentives he is offering, the government has dismantled much of the central or regional requirement for councils to build – leaving it to local initiative.

Shapps revealed he had been in discussion with Hughes over Cameron's plan to end tenancies for life.

Hughes has said the plan was not coalition policy and had not been in either party's manifesto. Opposition to the idea within his party is widespread. A total of 37 Lib Dem MPs signed an early day motion (EDM) in November 2007 which "actively opposes both the stigmatisation of council housing as housing of last resort and proposals to means test or time-limit secure tenancies".

Ten of the signatories stood down at the last election but 27 remain in the Commons. Add another five Lib Dem MPs who signed similar motions and defenders of security of tenure account for 32 of the current 57-strong parliamentary party.

The 2007 EDM was signed by two cabinet ministers: the energy and climate change secretary, Chris Huhne, and the Scottish secretary, Michael Moore. They were joined by Hughes and junior ministers in six other departments: Norman Baker (transport), Jeremy Browne (foreign affairs), Paul Burstow (health), Ed Davey (business), Lynne Featherstone (equalities) and Steve Webb (pensions).

The communities minister, Andrew Stunnell, joined Baker and Featherstone, two more backbenchers and many of the same MPs in signing an EDM in December 2008 that called on the government to fund "a new generation of first-class council housing to provide secure tenancies and low rents" that would allow local authorities "to open up their allocation policies once again to the wide range of people on council housing waiting lists so that butchers, bakers, nurses and teachers can live together with young families and pensioners, thus returning our estates to the mixed and sustainable communities they used to be".

Critics of Cameron say fixed-term tenancies would result in the opposite of mixed communities, with social housing becoming an option of last resort.

Education minister Sarah Teather, who held the housing portfolio before the election, was also a strong opponent of moves to end security of tenure.

Only five weeks ago, four Lib Dem backbenchers – Bob Russell, Mike Hancock, John Hemming and Mike Crockart – signed an EDM sponsored by Labour's Austin Mitchell which said: "The only way to allow for greater mobility of council and social housing tenants to enable them to move to where the jobs are, not to reduce the security of tenure to which tenants have a right, but to increase the stock of public housing so that it can not only cope with the increased demand but also allow for more mobility of tenants."